Cathode-ray tube with target controlled deflecting plates



W. A. MARRISON CATHODE-RAY TUBE WITH TARGET Sept. 12, 1950 CONTROLLED DEFLECTING PLATES 4 Sheets-Sheet 1 Filed Sept. 20, 1945 v: E 5 \w wwQ Q k m- G l- |Fl\ Tu Q b: h a? ily a\ //v VN 70/? 7 WA. MARR/SO/V Sept. 12, 1950 w. A. MARRISON 2,522,291

- CATHODE-RAY TUBE WITH TARGET CONTROLLED DEFLECTING PLATES Filed Sept. 20, 1945 .4 Sheets-Sheet 2 FIG. 5

FIG. 3

INVENTOR y WAMARR/SON B ew ATTORNEY W. A. CATHODE-RAY TUBE WITH TARGET MARRISON Sept. 12, 1950 CONTROLLED DEFLECTING PLATES Filed Sept. 20, 1945 4 Sheets-Sheet {5 IN [/5 N 7' OR MAMA/PRISON 2 mm a ATTORNEY Sept. 12, 1950 A. MARRISON W. CATHODE-RAY TUBE WITH TARGET CONTROLLED DEFLEC'IING PLATES Filed Sept. 20, 1945 FIG. 6'

4" Sheets-Sheet 4 mt-WW4 ATTORNEY Patented Sept. 12, 1950 OATHODE-RAY TUBE WITH TARGET CONTROLLED DEFLECTING PLATES Warren A. Marrison, Maplewood, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application September 20, 1945, Serial No. 617,631

20 Claims. 1

This invention relates to electrical signal translating devices and particularly to those of the electronic type.

Objects of the invention are to extend the field of usefulness of electronic devices and to make them more readily applicable to electrical systems for such purposes as selection, distribution, registration, repetition and for other signal translating functions.

Another object is to increase the accuracy, dependability and general utility of electronic beam devices.

The use of electron-beam tubes has been proposed heretofore for a wide variety of purposes in electrical systems particularly where sensitivity of control and high speed of operation are essential requirements. Among other proposals these tubes have been suggested for use as selectors, the variable incoming signal currents serving to control the movement of the beam to select a desired one of a plurality of electrodes to which suitable work circuits are connected. Since the precision with which the electron beam is moved over the object electrodes or into positions bearing desired relations with respect to said electrodes depends upon the signal and controlling currents or potentials applied to the control elements of the tube, any variation such as an increase, diminution, dissipation or other change in the magnitude of these currents or potentials will have its effect upon the movement and position of the electron beam. For example, it may be desirable in a beam selector to advance the electron beam under the control of incoming signals to a predetermined electrode and to hold the beam on such electrode as an indication of the selection made. If the signal potentials are too strong or too weak or if they tend to leak OE and dissipate, the beam will not be accurately positioned with respect to the electrode, or, if positioned accurately, it may gradually shift its position, thus impairing the efiect of the intended selection.

With the foregoing difficulties in mind, applicant has devised a novel means for securing and maintaining a high degree of precision in the operation of electron-beam devices. More specifically, applicant has devised an electron-beam tube in which special electrodes are provided for the purpose of preventing any unwanted deviation of the beam from its intended location with respect to the working electrodes of the tube. Once the beam has been moved into a desired position with respect to a Working electrode, it is accurately maintained in that position by the presence of said special or auxiliary electrodes. If for any reason it tends to depart from its proper position, potentials are established on the special electrodes which operate automatically to restore the beam to its proper position.

A feature of the invention is an electron tube having a coordinate field of selectable electrodes together with means for preventing the beam from deviating in any direction from a selected one of the electrodes on which it has been positioned. 7

Another feature of the invention is an electronbeam tube having electromagnetic means for correcting and adjusting the position of the beam with respect to the working electrodes.

The foregoing and other features of the invention will be discussed more fully in the following detailed specification.

In the drawings accompanying the specification:

Fig. 1 illustrates the invention when applied to an electron-beam tube having a single array of objective anodes;

Fig. 2 is an enlarged fragmentary view showing the relation between the beam and the electrodes;

Fig. 3 illustrates one possible arrangement of work circuits connected to the anodes of the tube;

Fig. 4 illustrates the invention applied to a tube having a coordinate field of obj ective anodes;

Fig. 5 is an end-view of the tube of Fig. 4 showing the field of objective anodes and a grid-work of auxiliary electrodes for correcting deviation of the beam; and

Fig. 6 is an alternative structure in which the correction of the beam is effected by electromagnetic means.

Referring now to the drawings and particularly to Figs. 1 and 2, the electron-beam translating device here illustrated includes a sealed.

vessel I00 containing means for developing a stream or beam of electrons and causing the beam to impinge selectively on any desired one of a series of objective anodes, The stream of electrons is developed by a cathode IOI and propagated by an accelerating anode I02 toward the forward end of the vessel or tube I00 where it is capable of engaging any one of a series of target controlled by a pair of deflector plates H3 and IM. By applying voltages of different values to the plates H3 and H4 the beam H2 is caused to advance to corresponding ones of the objective anodes I 04, I05, I06, etc. When the circuits are in their normal condition the beam IIZ rests on the normal anode I93 either by virtue of the disposition of the accelerating anode I82 or by a biasing voltage applied to the plates H3 and H4 in any suitable manner or by an additional set of control plates.

The forward end of the tube is also equipped with an auxiliary electrode, the purpose of which is to hold the beam in a selected position. This auxiliar electrode comprises a plate l I5, which is disposed behind the objective anodes I04, I55, I06, etc., and in such a position that the beam I'I'2 impinges on said electrode when it is not in full engagement with some one of the objective anodes. auxiliary electrode !!5 sets up a voltage, which depends for its magnitude upon the degree of exposure to the beam, and which is applied across the control plates I I5 and II! for the purpose of correcting the beam deviation.

It will be obvious that electron-beam devices of the type disclosed in Fig. 1 may be suitable for a Wide variety of purposes. In particular they are useful where it is desirable to store or register information, such as numbers or other charasters, for present or future use. Such an application is illustrated in Fig. l where incoming electrical impulses from a transmitting dial are received and translated by the tube into a corresponding position of the beam.

A description will now be given of the operation of the tube and its associated impulse circuit. When it is desired to transmit to the tube I09 a series of impulses representing a given number, the key H8 is operated to close an obvious. circuit for relay IISJ. Relay [I9 in turn closes an operating circuit for slow-release relay I26. The operator now manipulates the dial I2 5, for example, to the number nine position and upon release of the dial from this position, a series of nine impulses is transmitted. On the opening of the circuit for the first impulse relay H9 releases, but relay I20, being slow, maintains its armatures in their attracted position. A

charging circuit for condenser I22 may now be traced from the positive grounded pole of battery I25 over conductor I26, back contact I2? of relay I I9, condenser I22, contact-protective resistor I23, front contact I28 of relay I29 to the negative pole of battery I25. A definite predetermined charge is acctunulated on condenser I22 during the open period of the impulse. At the end of this first open period the dial contacts close and relay I I9 reoperates. The charged condenser I22 is now connected to the larger condenser I'ZI for the purpose of transferring its charge thereto. The circuit for this transfer may be traced from the upper terminal of condenser I22 through the front contact I29 of relay H9, front contact I38 of relay I20, condenser I2I, resistor I23 to the opposite terminal of condenser I22. Upon the next opening of the dial contacts relay I I9 releases, and condenser I22 is recharged for the second impulse. When the dial contacts close at the end of the second impulse, relay H9 operates, and the charge on condenser I22 is transferred to condenser I2! where it is added to the charge representing the previous impulse. In like manner, each of the succeeding impulses re- The impingement of the beam on the 4 sults in the addition of an incremental charge to the condenser I2I.

It will be noted that the condenser I2! is connected across the control plates H3 and H4, wherefore the increasing charges applied to the condenser cause the application. of increasing voltages to said control plates. Each of these voltage increments is just sufiicient to advance the electron beam I I2 from one anode to the next. That is to say, the voltage applied to plates H3 and N l in response to the first impulse causes the beam H2 to move from the normal anode N33- to the No. lanode Hit, the increased voltage resulting from the second impulse causes the beam to move from anode HM to the No. 2 anode I85, and likewise for each succeeding impulse until the beam H2 is finally brought to rest on the No. 9% anode I88.

By careful design it is; possible to derive voltage values that will bring the beam I I2 into accurate relationship with the successive objective anodes. However, it is sometimes desirable to permit tolerable variations in the manufacturing of apparatus, and it is also well known that condenser charges have a tendency to leak away with time. With these considerations in mind it will be seen that the beam I I2 ma not always occupy a fully centered relationship with respect to the objective anode to which it has been driven. Assume, for example, that the charge on condenser I2I,

which drives the beam to one of the objective anodes, such as anode Hi5, gradually becomes diminished as a result of leakage. As the charge diminishes, the beam I H slowly returns towards its normal position and in so doing impinges to some extent On the auxiliary electrode i I5. This relationship is. more clearly illustrated in Fig. 2. A circuit may now be traced from the positive pole of battery I25, deflector plates H6 and- Ill, conductor I26, auxiliary electrode I I5 thence over the beam H2, cathode IDI to the negative pole of battery 125. The voltage applied to plates H6 and II! in this circuit is of such a polarity that it prevents further downward movement of the beam and thus prevents it from wandering off the anode I85. It will be noted from Fig. 2 that the greater the deviation of the beam the greater the exposure on the electrode H5 and consequently the more pronounced is the restoring potential applied to the plates I It and I IT.

The objective anodes I'M, I85, E55, etc, may be connected to any suitable type of work circuit. In the drawings resistors are illustrated, and in Fig. 3 the voltages developed in these resistors serve to operate responsive devices such as discharge tubes 309, 35H, etc. To consider the example chosen, it the beam 382 is driven to the No. 9 objective anode 353, the current flowing by way of the beam and anode 353 throughresistor 3M develops a voltage which is applied across the control electrodes of the tube 300. This voltage causes the tube to ionize, whereupon current fiows from the positive pole of batter 305, resistor 3&6, across the anode-cathode gap of the tube 355 thence to ground. The voltage developed in the resistor 306 may be used for any suitable purpose such as indication or control.

It will be noted that the beam I I2 may impinge briefly on the auxiliary electrode H5 as it steps from. one objective anode to the next. of course, is not objectionable since the voltage developed by the engagement of the beam with the electrode 5 E 5 is in the direction to move the beam When it is desired to release the beam after it 1 has served its purpose, key H8 is opened, and relay II9 releases and opens the circuit of relay I20. After an interval relay I20 releases and in so doing closes a short circuit around the condenser I2I. Condenser I2I becomes fully discharged, and the beam II2 returns to its normal position anode I03.

The tube 400 shown in Figs. 4 and is provided with a coordinate field of objective anodes, and the beam 40I is driven in two coordinate movements to select any desired one of the anodes. The number of anodes may be chosen to suit the requirements; for example, the field may include 100 anodes arranged in ten rows of ten anodes per row. In the drawings only twenty anodes 402, 403, 404, 405, etc., have been shown for the sake of simplicity.

The beam 40I is driven in a vertical direction by means of deflector plates 4 and M2 for the purpose of selecting a horizontal row of anodes and is driven horizontally by deflector plates M3 and M4 to select a particular anode in the horizontal row. The voltages for driving the beam are supplied to plates 4| I4l2 and 4I3-4I4 over circuits M5 and M6.

Once the beam is positioned upon a selected anode it is held in position and prevented from deviating in any direction by means of four auX- iliary electrodes M1, M8, M3 and 420. Each one of these auxiliary electrodes includes a plurality of parallel extensions which collectively form a frame or boundary for each of the individual objective anodes, as seen in Fig. 5. For example, the anode 406 is bounded on the right by the extension 42I of electrode 420, on the left by extension 422 of electrode M9, on the upper side by extension 423 of electrode 4H, and on the lower side by extension 424 of electrode 4I8. Electrode 4 I I is connected to plate 425 of the pair of vertical deflecting plates 425426, which serve to apply a vertical correction to the beam in one direction. Similarly the auxiliary electrode M8 is connected to plate 428 of the pair of vertical deflecting plates 427-428, which serve to apply a vertical correction in the opposite direction. Auxiliary electrode 4I9 is connected to plate 429 of the pair of horizontal deflecting plates 429430, which serve to apply a horizontal correcting movement of the beam to the right as seen in Fig. 5. Similarly the electrode 420 is connected to plate 432 of the pair of horizontal deflecting plates 43I432, which serve to apply a horizontal correcting movement of the beam to the left.

To explain the operation of the translating tube shown in Fig. 4 assume that a voltage is applied over circuit 4 I 5 to the deflector plates'4I I and 4 I 2 and that this voltage is suflicient to move the beam in a vertical direction to the third horizontal row of objective anodes. Assume also that a voltage is applied over circuit 4I6 to theplates4I3 and 4M and that this voltage is sufilcient to deflect the beam along the selected horizontal row until it engages the desired anode 406. In this position of the beam the work circuit may be traced from the negative pole of battery 433,

cathode 434, beam 40I, anode 406, resistor 435. to the grounded positive pole of battery 433. The

voltagedeveloped in the resistance 435. may-be used-for any suitable purpose.

If during the time the b'eami40I' is positioned on the anode 406 the voltage'on the'deflecting plates 4ll and M2 varies in such a manner as to cause the beam to digress upwardly, a portion of the beam will engage the extension 423 on the auxiliary electrode 4I'I. This engagement of the beam with theauxiliary electrode causes a correcting voltage to be applied to the plates 425 and 426 over a circuit which may be traced from the positive pole of battery 433, conductor 436, plate 426, plate 425, auxiliary'electrode 4II, beam 40I,

cathode 434 to the negative pole of battery 433. The polarity of the voltage thus applied to the plates 425 and 426 is such that the beam is returned downwardly to'itsproper position with respect to the anode 403. On the other hand if the voltage across the plates M I and 4I2 varies in the opposite sense, the beam 40I digresses in a downward direction andencounters the extension 424.

on the electrode 4 I8. A circuit is now closed, similar-to the one above traced, for applying a correcting voltage to the deflector plates 42! and 428. In" this case, howeventhe correcting voltage is. of the opposite polarity and acts on the beam to return it in an upward direction to its centered position on the anode 406. Should the voltage on the plates 4 l 3 and II 4 increase somewhat in magnitude, the beam 40I is diverted to the right and engages the extension 42! on the electrode 420. This applies a correcting voltage to the plates 43I and 432 of a polarity to restore the beam to its correct position. Likewise a reduction of the voltage on plates 413 and M4 permits the beam to deviate to the left where it engages the extension 422 on the electrode M9, and a correcting.

voltage of the opposite polarity is applied to the plates 429 and 430 for restoring the beam.

In the modification disclosed in Fig, 6 of the drawing the correction of the beam is accomplished by means of an electromagnetic field.

1 Normally the beam rests on the normal position anode 602. When a voltage is applied to the deflector plates 603 and 604, the beam is driven over the objective anodes 605, 303, 601, etc., until it comes to rest on the desired one of these anodes. If the beam deviates from its position on the selected anode and consequently engages the auxiliary electrode EHO, a circuit is established from the negative pole of battery 6| I, cathode 6I2, beam 30!, electrode 6I0, conductor 3I3 thence in parallel through resistor 320 and condenser 6I4 to the positive pole of battery GI I. The condenser 6I4 acquires a charge in this circuit, the polarity of which opposes the biasing battery 6I5 and causes the tube '3 I 6 to conduct. Current now flows over a circuit traceable from the positive pole of battery SI 1 through the coils 6 I8 and BIB; anode and cathode of tube BIB thence in parallel through condenser 3| 4 and resistor620 to the negative pole of battery M1. The current flowing in coils (H8 and GIS sets up a magnetic field ascaaci 7 \l/lietisclaimed is: i1. An electronic beam device comprising a plurallity of target anodes, means opposite said anodes for projecting an electron beam thereto, auxiliary electrode means adjacent and laterally beyond said anodes for intercepting electrons in said beam directed to pass by said anodes, means for driving said beam over said anodes, and means for efiecting a definite relation between said beam and a particular one of said anodes comprising means for deflecting said beam and coupled to said auxiliary electrode means to be controlled in accordance with the beam current impinging upon said auxiliary electrode means.

2. An electrical beam device comprising a plurality of fixed electrodes arranged in spaced relation, means opposite said electrodes for producing a beam of energy for engagement with said fixed electrodes, an auxiliary electrode adjacent and so disposed with respect to said fixed electrodes that said beam impinges on said auxiliary electrode when it is not in full engagement with some one of the fixed electrodes, means for moving said beam into engagement with a predetermined one of said fixed electrodes, and means responsive to the impingement of the beam on said auxiliary electrode in the event the beam fails to fully engage the predetermined fixed electrode for automatically adjusting the position of the beam in the direction of full engagement with said predetermined electrode, said means comprising beam control deflecting means activated by the energy derived from the beam by the auxiliary electrode.

3. An electrical beam device'comprising a plurality of fixed electrodes arranged in spaced relation, means opposite said-electrodes for producing a beam of energy for engagement with said electrodes, means for moving said beam into engagement with a particular one of said electrodes, auxiliary electrode means adjacent said electrodes for deriving energy from said beam in response to its departure from a predetermined relation with said particular electrode, and'beam deflecting means for utilizing the energy derived from said beam by said auxiliary electrode means for automatically reestablishing said predetermined relation.

.4. .In an electrical beam device, a plurality of electrodes arranged in spaced relation, means opposite said electrodes for producing a beam of energy .for engagement with said electrodes, means for moving said beam into a position to engage a particular one of said electrodes, means comprising an auxiliary electrode effective only when said beam recedes from a prescribed position of engagement with said particular electrode for deriving from the beam an amount of energy proportional to the recession,-and beam deflecting means utilizing the energy derived from said beam by said auxiliary electrode means to restore the beam to its position of engagement with said particular electrode.

5. In an electrical beam device, a plurality of electrodes disposed in a coordinate field, means opposite said electrodes for producing a beam of energy for engagement with said electrodes, means for moving said beam into a position to engage a predetermined one of said electrodes,

and beam deflecting means cooperating with auxiliary electrode means responsive to the departure in any direction of said beam from its position of engagement for restoring said beam to its said position of engagement with said predetermined electrode, said auxiliary electrode means having portions laterally beyond said electrodes.

6. An electrical beam device comprising aplurality offixe'd electrodes arranged in a coordinate field, meansopposite said electrodes for producing a 'beam of energy ,for'engagement with said fixed electrodes, a plurality of auxiliary electrodes 'bordering'each of said fixed electrodes and subject to engagement by said beam of energy, means for driving said beam into engagement with a predetermined one ofsaid fixed electrodes, and beam deflecting means including said auxiliary electrodes and effective in response'to the engagement of the beam with said auxiliary electrodes for maintaining said beam in its position of engagement with said predetermined fixed electrode.

'7. The combination in a translating device of a plurality of fixed'electrodes, means for producing a beam of energy for'engagement with said electrodes, means for moving said beam to selectively engage a predetermined one of said electrodes, and electromagnetic means responsive to a departure of said beam from its position of engagement with said predetermined electrode for maintaining said :beam in engagement with said predetermined electrode.

8. .An electronic beam device comprising a sealed envelope, a series of fixed anodes arranged in spaced relation within said envelope, acathode within said envelope for developing a beam of electrons for engagement with said fixed anodes, electrostatic deflector plates Within-said envelope for driving said beam into engagement with a predetermined one of said anodes, an auxiliary anode mounted in proximity to said fixed anodes and subject to engagement by said beam as it passes from one anode to another, a second set of deflector plates, and means =-comprising a feedback coupling from said auxiliary anode to saidseconddeflector :plates effective ifrsaid beam departs from its position of full engagement with said predetermined anode and into engagement with said auxiliary anode for applying a.,potential to said second set'of deflector plates for the purpose of restoring said beam to its position of full engagement with said predetermined anode.

9. .Anelectrical beam device comprising a plurality of target :anodes, means opposite said anodes for projecting a beam of energy thereto, means for causing movement'of said beam relative to said target anodes and for .positioningsaid beam in engagement with a predetermined one of said target anodes, and means for maintaining said beam positioned on said target anode comprising an auxiliary electrode for intercepting said beam when it departs from said target anode and beam deflecting means coupled to said auxiliary electrode and energized by the beam energy intercepted by said auxiliary electrode.

10. An electrical 'beam device comprising means .for producingalbeam of energy, a target anode opposite said means, means for deflecting said beam to .a positionof=engagement upon said target anode, an auxiliary electrode adjacent said anode and placed so that said beam impinges upon it when not in .full engagement with said target anode, and deflecting means coupled to said auxiliary electrode for exerting a restoring force upon said beam in proportionto the-degree of exposure of said auxiliary electrode to said beam.

11. An electronic beam device comprising means for producing a beam of electrons, a series of target anodes opposite said means located in a line, means for moving said beam along said line of anodes, auxiliary electrodes subject to impingement by said beam, located on both sides of and parallel to the line of said target anodes, and means for restricting the movement of said beam to a path between said auxiliary electrodes comprising beam deflecting means electrically connected to said auxiliary electrodes and energized when the electron beam deviates from said path to impinge upon one of said auxiliary electrodes.

12. An electronic beam device comprising means for producing a beam of electrons, a plurality of target anodes opposite said means, a plurality of auxiliary electrodes positioned relative to said target anodes to form a frame about each target, means for positioning said beam substantially within the frame of any one target, and beam deflecting means energized when said beam impinges upon any of said auxiliary electrodes for moving said beam towards a centered position within said frame.

13. An electrical beam device comprising means for producing a beam of energy, a group of target areas opposite said means, auxiliary electrodes adjacent said target areas, means for moving said beam into one of said target areas, and deflecting means energized when said beam tends to drift out of said target area, into impingement with an adjacent auxiliary electrode, for retaining said beam within said target area.

14. An electrical beam device comprising means for producing a beam of energy, a group of target areas opposite said means and bounded by auxiliary electrodes, means for positioning said beam on any one of said target areas, and deflecting means energized when said beam drifts from its position with respect to said target area, into impingement with a boundary auxiliary electrode, for containing the beam substantially within the target area.

15. An electron discharge device comprising a target having an edge extending in one coordinate direction of a two coordinate plane system, means opposite one face of said target for projecting an electron beam thereto, means for deflecting said beam in the second coordinate direction, and means for controlling the position of said beam in said second direction to position said beam upon said target, said controlling means comprising an auxiliary electrode opposite the other face of said target and extending beyond said edge to intercept electrons in said beam which pass beyond said target and a feedback connection between said auxiliary electrode and said deflecting means.

16. An electron discharge device comprising a plurality of imperforate targets having corresponding edges extending in one coordinate direction of a two coordinate plane system, means to one side of said targets for projecting a concentrated electron stream thereto, means for defleeting said stream in the second coordinate direction of said system, and means for controlling the position of said stream in said second direction, said controlling means comprising means to the other side of said targets and responsive to electrons in said stream which pass to said other side, and connected in feedback relation to said deflecting means.

17. An electron discharge device comprising target means including a plurality of imperforate elements having corresponding edges extending in one coordinate direction of a two coordinate plane system, means to one side of said target means for projecting a concentrated electron stream to said elements, means fordeflecting said stream in the second coordinate direction of said system, and means for controlling the position of said stream in said second direction, said controlling means comprising electron receiving means to the other side of said target means and extending beyond said edges to intercept electrons in said stream which pass by said edges, said controlling means comprising also a direct conductive feedback circuit between said electron receiving means and said deflection means energized proportionately to the stream current to said electron receiving means.

18. An electron discharge device comprising a row of imperforate target electrodes having corresponding edges extending substantially normal to the direction of said row, means to one side of said target electrodes for projecting a concentrated electron stream thereto, means for deflecting said stream in said direction to selectively direct said stream to impinge upon any one of said target electrodes, and means for controlling the deflecting force due to said deflecting means comprising auxiliary electrode means mounted to the other side of target electrodes and extending beyond said edges to intercept electrons in said stream which pass by any of said edges, said controlling means comprising also a direct conductive feedback connection between said auxiliary electrode means and said deflecting means.

19. An electron discharge device comprising a plurality of targets mounted in a row, an auxiliary electrode having a portion laterally adjacent one side of said targets and extending in the direction of said row, means opposite said targets for projecting an electron beam thereto, a first deflecting means for deflecting said beam over said targets inv said'direction, a second defleeting means for deflecting said beam normal to said direction, and means for controlling the position of said beam in said normal direction comprising said auxiliary electrode, said second deflecting means and a feedback coupling between said auxiliary electrode and said second deflecting means.

20. An electron discharge device in accordance with claim 19 comprising a second auxiliary electrode laterally adjacent the other side of said targets and extending in the direction of said row, and wherein said controlling means comprises a third deflecting means for deflecting said beam in said normal direction and a feedback coupling between said second auxiliary electrode and said third deflecting means.

WARREN A. MARRISON.

REFERENCES CITED The following references are of record in the file of this patent:

, UNITED STATES PATENTS Number Name Date 2,190,069 Hollmann Feb. 13, 1940 ,677 Hanscom Dec. 10, 1940 ,287, 96 Dallos June 23, 1942 0 ,617 Hansel Dec. 22, 1942 3 9 Ziebolz et a1 Sept. 12, 1944 9 Skellett Feb. 19, 1946 ,404,106 Snyder July 16, 1946 2,417,450 Sears Mar. 18, 1947 45 Morton Aug. 10, 1948 

